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From DNA to Protein

From DNA to Protein. Chapter 8. Terminology. Genetics Genome Chromosome Gene Locus Alleles Genotype/Phenotype Heredity. Living cells must accomplish two general tasks to multiply and survive DNA replication Gene expression Expression involves two process Transcription Translation

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From DNA to Protein

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  1. From DNA to Protein Chapter 8

  2. Terminology • Genetics • Genome • Chromosome • Gene • Locus • Alleles • Genotype/Phenotype • Heredity

  3. Living cells must accomplish two general tasks to multiply and survive • DNA replication • Gene expression • Expression involves two process • Transcription • Translation • Flow of information from DNA to RNA to protein

  4. DNA • Polymer of nucleotides • Hydrogen bonds between complementary bases • AT and CG • Antiparallel • New nucleotides can only be added to the “free” 3’ end

  5. DNA synthesis involves anabolic polymerization Monomers (Triphosphate deoxyribonucleotides) provide required energy for DNA synthesis

  6. One DNA double helix. • Replication produces two DNA double helixes • Each contains one original strand and one new strand Semi-conservative DNA replication Two identical DNA double helixes, each with one parental strand (blue) and one new strand (pink).

  7. DNA replication in bacteria is bi-directional • due to closed circular chromosome • replication forks eventually meet and two complete loops are separated

  8. Bacterial DNA is attached at several points to the cell membrane • Enzymes need for replication are membrane proteins

  9. Topoisomerase (DNA gyrase) • Helicase • Primase • DNA polymerases • DNA Ligase

  10. Bacteria replication involves methylation of daughter stands • Methylase • Adds methyl group (-CH3) to nitrogenous bases (typically adenine) • Methylation functions: • Initiation of DNA repliction • Control of genetic expression • Protection from viral infection • Repair of DNA

  11. DNA Replication • As DNA unwinds, it creates a replication fork • As nucleotides are added, the replication fork moves down the parental strand

  12. Leading strand • Is synthesized CONTINUOUSLY as the DNA polymerase moves towards the replication fork • Lagging strand • Is synthesized DISCONTINUOUSLY in pieces as DNA polymerase moves away from the replication fork • Okazaki fragments

  13. Single Strand Binding Proteins

  14. DNA contains the instructions for protein synthesis • Genes • RNA carries out the instructions • Genetic information flows from DNA to RNA to protein

  15. Central Dogma of Molecular Biology • DNA Transcribed RNA • RNA Translated Protein

  16. Gene Expression • Transcription • RNA polymerase synthesizes complementary mRNA from DNA template • Cytoplasm of prokaryotes and the nucleus of eukaryotes

  17. Concurrent RNA transcription Multiple copies of RNA can be transcribed simultaneously

  18. Eukaryotic DNA is more complex • Requires post-transcriptional modifications • Spliceosome • Cap and tail

  19. Translation • The language of mRNA is in the form of codons • Three nucleotides situated next to each other on DNA • Sequence of codons determines sequence of amino acids in the protein • 64 codons make up the “alphabet” • 61 are sense codons • 3 “stop codons”

  20. The site of translation is the ribosome

  21. tRNA brings appropriate amino acid to site of translation • Each tRNA has an anticodon • complementary sequence to the mRNA codon

  22. In a prokaryotes, many molecules of mRNA can by transcribed simultaneously • Why can translation begin before transcription is completed in a prokaryote but not in a eukaryote?

  23. gene DNA complementary DNA strand template DNA strand codons mRNA anticodons tRNA amino acids protein methionine glycine valine

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